A typical railroad switch has a pair of point rails movable into and out of engagement with respective stock rails for diverting a train on the stock rails to a siding or other track. Each of the point rails is moved by a roller assembly comprising a support carrying at least one roller and resiliently supported on a rail base plate formed as a slide plate or slide chair. The point rail is supported on the roller at least during a switching process.
Roller assemblies designed in such a manner are well known from the prior art and allow the point rail to be slightly lifted during the opening or switching process and therefore not in contact anymore with the slide chair or the slide surface of the rail base plate. In so doing, the point rail moves over a roller or rolling bodies that effect a significant reduction of the switching forces and allow the slide chairs or slide surfaces to be lubricant-free.
For an accurate height adjustment of the uppermost tangent plane of the rollers, the same are resiliently mounted as described, for example, in DE 295 09 542.
The roller mounting has a pure load-bearing function here during the switching process so that the point rail, in the position in which it abuts against the stock rail, rests on the slide chair or the slide surface of the rail base plate.
In this so-called closed state, the point rail bears within the switch arrangement with its point tip against the stock rail and with its root region or point rail web against support cleats or spacer blocks. After a long period of use, i.e. by running many times over the point rail with the full wheel load in the root region, the given or pre-bent shape of the point rail changes in the longitudinal direction of the rail. As a result of the shape change, the point rail no longer comes into abutment in the web region with the support cleats or spacer blocks. When running over the point rail, this state can result in significant wear on the slide chairs or the slide surfaces of the rail base plates because the point rail is brought in an undesirable manner into abutment against the support cleats only by the transverse force of the wheel running over the point rail. Here, very significant friction forces occur between the bottom side of the point foot and the slide chair or the slide surfaces of the respective rail base plates as a result of the additionally vertical vector of wheel force.
In order to avoid this disadvantage it became known from EP 0 654 561 [U.S. Pat. No. 5,509,626] that a roller support having at least one holder for at least one roller is mounted to resiliently move in a direction toward the stock rail, the point rail abutting via the roller against the stock rail and therefore, the resistance during the movement of the point rail is kept low.
To this end, the roller is partially slid underneath the point rail by a leaf spring. Spacers make it then possible to adequately fix the roller against the force of a separate spring and in abutment against the foot of the point rail.
This roller assembly is mounted via the leaf springs and retaining elements provided at its ends on two adjacent switch sleepers of a track bed and therefore lies in the center of the space between two sleepers.
As a result, the roller assembly projects into the tamping region for ballast underneath the switch sleepers. This means that the roller assembly has to be disassembled prior to tamping the ballast, then reassembled and subsequently readjusted.
Further, this roller assembly can only be assembled after the switch system has been installed on site. This results in work-related additional expenses and time delays on the construction site.